Field of the Invention
The present invention relates to the field of radiofrequency (RF) ablation apparatuses and methods, and more specifically, to retractable, multipurpose, multi-tined RF cannulae and probes for the application of RF energy to tissue for therapeutic purposes.
Description of the Related Art
Radiofrequency (RF) energy can be applied for therapeutic pain management not relieved by conservative medical procedures by insertion of insulated cannulae with a bare metal tip into a target area of tissue such as neural structures centrally in a spinal space, paravertebral space, or an epidural space, or peripherally into spinal nerves or ganglia. Additional neural targets include intervertebral disc nerves within the disc nucleus or annulus fibrosis. RF energy can also be used for tumor ablation in structures such as the liver or bone. The RF energy can be applied in a continuous or pulsed manner. Both generally use sinusoidal waveforms at about 500 KHz, but the difference is that continuous RF applications are, as the name implies, continuous or uninterrupted, whereas pulsed RF consists of bursts or pulses of the same sinusoidal RF waveform separated by inactive or rest periods between pulses. A typical protocol for pulsed RF is two pulses per second, each lasting 20 milliseconds, with rest periods of 480 milliseconds between pulses.
Regardless of the RF modality—continuous or pulsed—a problem has been reliably and predictably conforming the ablation size, shape, and orientation to that of the tissue target, exactly for neural destructive procedures where unwanted extension may cause collateral damage to other, important neural structures, or purposely beyond the target in tumor destruction to create a margin of safety to include isolated regions of tumor extension. Too cautious an approach for neural destructive procedures to minimize the possibility of collateral nerve damage in pain management or the destruction of functional normal tissue in tumor ablation will, unfortunately, contribute to either less than optimal outcomes or procedure failures. Overcoming these deficiencies requires innovation in RF probe design that allows the deployment of multiple tined electrodes that can uniquely adapt their curvature and direction, and their extruded length, to generate RF lesions conforming to tissue target shape and orientation, and a size that best assures therapeutic efficacy and safely.